Experimental and numerical investigation on shale fracture behavior with different bedding properties

Bo, Lei; Zuo, Jianping; Liu, Haiyan; Wang, Jintao; Xu, Fei; Li, Hongtao

doi:10.1016/j.engfracmech.2021.107639

Cited by 35 publications

(13 citation statements)

References 28 publications

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“…Shale gas is an unconventional clean energy. In recent years, it has become a new research hotspot in the energy industry (Lei et al, 2021;Bilgen and Sarıkaya, 2016;Meakin et al, 2013;Wang and Li, 2017). Shale gas resources in China are widely distributed, with the advantages of large resource reserves, high energy conversion rate and low pollution index.…”

Section: Introductionmentioning

confidence: 99%

“…The results showed that the mechanical properties of weak laminar planes had significant effects on fracture mode, tensile strength, fracture toughness, crack initiation angle, crack extension path and complex fracture network generation (Lei et al, 2021). Guo et al conducted static and dynamic compressive tests on dry and water-saturated shale specimens with bedding dips of 0°, 30°, 45°, 60°, and 90°.…”

Section: Introductionmentioning

confidence: 99%

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3D parallel numerical simulation of bedding-containing shale based on CT technology and digital image processing

Zuo

et al. 2023

Preprint

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The aim of this study is to investigate the effect of bedding inclination on the tensile strength and damage mechanism of shales. In this paper, we obtained images of shale specimens from the Lower Cambrian Niutitang Formation in the northern part of Guizhou Province by CT scanning, reconstructed 3D numerical models of shale at 0°, 30°, 45°, 60° and 90° bedding inclination angles using RFPA-3D finite element software, and performed direct tensile simulation tests. The test results show that the anisotropic nature of the tensile strength of the shale exhibits significant. The tensile strength reaches a minimum value of 2.97 MPa at θ = 0° and a maximum value of 5.27 MPa at θ = 90°. Shale specimens exhibit two modes of damage under uniaxial tension: a mode of damage by tension along the bedding and a mode of damage by compound tension along the bedding and the shale matrix. The spatial distribution of the acoustic emission points better reflects the macroscopic damage pattern of the specimen, and the acoustic emission counts show a single-peak distribution. The research is an important reference for shale reservoir hydraulic fracture sprouting, extension prediction and recovery enhancement.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

3D parallel numerical simulation of bedding-containing shale based on CT technology and digital image processing

Zuo

et al. 2023

Preprint

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“…Due to simple operation and easy machining, a three-point bending experiment is always used to measure the fracture toughness of materials. Numerous scholars have studied the effects of sample size [30], incision-to-depth ratio [31][32][33], loading rate [34], temperature [35,36], and bedding angle [37,38] on the fracture parameters of quasi-brittle materials. Agioutantis et al [8] through the acoustic emission technology detected the crack evolution of marble under three-point bending conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Agioutantis et al [8] through the acoustic emission technology detected the crack evolution of marble under three-point bending conditions. Zuo et al [35,37] was based on a three-point bending experiment to study the tensile strength and fracture toughness of small-scale rock samples under different temperatures and joint conditions, and SEM was applied to observe the initiation and propagation of micro cracks simultaneously, which is of great significance to understand the formation of macroscopic visible cracks. However, there are few studies on the mechanical properties and crack propagation of small-scale coal samples under a three-point bending test.…”

Section: Introductionmentioning

confidence: 99%

Multiscale Pore Structure Characteristics and Crack Propagation Behavior of Coal Samples from High Gas Seam

Zhu

Shao

et al. 2022

Materials

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Investigation on the pore-fracture features and crack propagation behavior of coal is necessary to prevent coal mine disasters. The pore structure features of coal samples taken from high gas seam were obtained by mercury injection porosimetry (MIP) and gas adsorption methods. The process of deformation and failure for coal samples under three-point bending conditions were obtained. The results demonstrate that the adsorption pores with diameter less than 100 nm are the most developed and their surfaces are the roughest (the average surface fractal dimension Ds is 2.933). The surface of micro-cracks is smoother (Ds is 2.481), which is conducive to gas seepage. It may be the explanation for that 14-3# coal seam is a high gas seam, while there was almost no gas outburst accident so far. At the initial stage of crack propagation, the main crack on the coal sample expanded along the direction of the natural cracks. In the process of crack propagation, the surface fractal dimension of the main crack increased, suggesting that the bending degree of the main crack enhanced. The brittle characteristics of coal samples can be reflected by the ratio of the dissipated energy to the accumulated energy.

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“…In addition, combining specimen splitting, CT scanning, and acoustic emission (AE), Ma et al [38] discussed the geometry of hydraulic fractures and influences of bedding plane on fracture initiation and propagation. Bo et al [39] observed the micro fracture process of shale under the three-point bending load with SEM, showing that the branch cracks have the tendency of connecting with the main crack. Also, its propagation length is relied on crack propagation resistance and propagation energy.…”

Section: Introductionmentioning

confidence: 99%

The Investigation on Initiation and Propagation of Hydraulic Fractures in Shale Reservoir

Liu

Lei

Huang³

et al. 2021

Geofluids

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Hydraulic fracturing is a necessary technique for shale gas exploitation. In order to have efficient stimulation treatment, a complex fracture network has to be developed, whereas with rich bedding planes and natural fractures, the mechanism of forming a fracture network is not fully understood and it is so tricky to predict propagation and initiation of hydraulic fracture. Therefore, in this paper, considering the strong anisotropy of shale reservoir, numerical simulation has been conducted to analyze fracture propagation and initiation on the basis of finite element and damage mechanics. Simulation results indicate that hydraulic fracture is not merely controlled by in situ stress due to strong anisotropy in shale. With plenty of bedding planes, hydraulic fracture tends to have initiation and propagation along the bedding plane. In particular, this influence becomes stronger with low strength and high development density of bedding planes. Additionally, in combination with natural fracture and bedding plane, the initiation point is usually on a natural fracture plane, causing relatively small breakdown pressure. In the process of fracture propagation, hydraulic fracture connects with natural fractures and bedding planes, forming dendritic bifurcation and more complicated paths. Numerical simulation proves that bedding plane and natural fracture are vital factors of hydraulic fracture. Compared to natural fracture, the bedding plane has a stronger impact on hydraulic fracture propagation. For the initiation of hydraulic fracture, natural fracture is the major effecting factor. The outcome of this study is able to offer theoretical guidance for hydraulic fracturing in shale.

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Experimental and numerical investigation on shale fracture behavior with different bedding properties

Cited by 35 publications

References 28 publications

3D parallel numerical simulation of bedding-containing shale based on CT technology and digital image processing

3D parallel numerical simulation of bedding-containing shale based on CT technology and digital image processing

Multiscale Pore Structure Characteristics and Crack Propagation Behavior of Coal Samples from High Gas Seam

The Investigation on Initiation and Propagation of Hydraulic Fractures in Shale Reservoir

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